Green Screen

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How do you move characters around in a world that lives only in your
imagination? By following this easy step-by-step guide to going green.
Through the magic of video effects and technology, you can superimpose
your subjects onto virtual backgrounds, place them over animated digital
backdrops or transport them to a desert oasis. You can shrink down a
full-grown man so he can stand on a tabletop, use visual effects to make
him fly through the sky like a superhero or simply simulate your own TV
weather report. But to do it right, you're going to need a lot of green.
No, we're not talking about money. The green we mean comes in the form
of a green screen. The secret to pulling your subject out of the real
world and placing him or her into a digital domain ischromakey,
and that means going green. In this article we'll cover all the
essentials you need to know to pull off keen, clean keys and composite
digital backdrops and virtual backgrounds into your edits.

What is Keying?

Keying is the process of isolating a single color or
brightness value in an electronic image and using software to make that
value transparent, allowing another image to show through the affected
areas. Luminance keying, or lumakeying, is the process of keying out a
brightness value or range, like black or white. Luminance keys are often
used for applying mattes. Color keying, or chromakeying, identifies a
specific color to remove.

Why Green?

Many people use the terms chromakeying and green
screening
interchangeably, but the principle that powers chrominance keying is not
limited to the green parts of the spectrum. In the visual effects world
of Hollywood, blue screens are far more common than green. In fact, you
can key out any color; red, yellow, purple or pink, blue and yes, green.
So why is that odd and ugly shade of green the hue of choice for
television and video? The biggest factor is contrast. In order to
isolate one area from the rest, the background color must be distinctly
different. Bright green beats blue partially because it is not a color
commonly worn by talent. Any clothing that matches the background too
closely will also key out, punching a hole in your subject's body, or
making him invisible altogether. We narrowly escaped a chromakey crisis
a few years ago when I was working at a Northern California TV station.
One St. Patrick's Day our wacky weatherman showed up to work dressed
head-to-toe in a bright green leprechaun suit. Fortunately, we quickly
pointed out the flaw in his logic and he was able to find a change of
clothes before it was time to go live.

What do I Need?

You can erect a simple chromakey setup almost anywhere
with just a few basic tools. In order to shoot footage that will key
cleanly, you will need a green background, a source of bright, even
lighting, and a tripod to lock your camcorder in place. We will cover
each of these elements in detail.

The most obvious need is for the background itself.
Fortunately, there are many options, and many of them are inexpensive.
In short, anything that's bright green will work, and anything that
works is valid. I have produced professional green screen scenes using
giant dedicated cyclone sets, large professional fabric chromakey
backdrops, sheets of material purchased by the yard from a fabric store,
smooth walls or pieces of paneling painted with a gallon of
dinosaur-green paint from the kids section of the hardware store, even
sheets of green poster board taped together. (NOTE: Be sure to avoid
textured walls if you're painting it green. Texture causes shadows.) The
only requirements are that your background be large enough to fill your
screen, smooth enough to take light evenly without showing wrinkles or
casting shadows, and bright enough to contrast well with your subject.
If you intend to chromakey a sock puppet your backdrop may be relatively
small. If you need to chromakey a full-body shot of an adult actor, you
will need a much larger background. If you are experimenting with
chromakeying for the first time, you can test the process on a small
scale before you build a big set. You can quickly create a functional
miniature table-top set with an action figure and a sheet of posterboard.
It doesn't take much more effort, however, to stretch a sheet of green
fabric between two step ladders or to paint a small section of wall.

Many people use the terms chromakeying and green
screening
interchangeably, but the principle that powers chrominance keying is not
limited to the green parts of the spectrum.

Even a professional-quality cyc wall won't key well
without proper lighting. If there is a secret technique to getting good
keys, it is in lighting the wall. The goal is to light the set as evenly
as possible using soft light. Any variation in lighting will read as
gradient coloring and will complicate your key in post. Achieving even
lighting can be more difficult than you might think. Hard light sources
cast narrow and focused beams that create circular hot spots in their
center, then fall off rapidly leaving outer portions gradually darker.
It helps to move small lights farther away so they cast broader, soft
light beams. If you have access to soft boxes, they are excellent
options for casting evenly spread light. I have had great success
lighting green screens with long tubular fluorescent fixtures along the
top and sides of the backdrop. You can get a six-foot garage-style
fixture from your local home hardware store for less than lunch. These
fixtures cast a soft light that is quite appealing for your green
screen. You don't want to light your talent with a flo-fixture, but when
you are lighting a green set the color temperature of the instrument is
not as important as lighting your background evenly.

Another important, but often overlooked, essential is
lighting your subject independently of your set. This is important for
two "key" reasons: shadows and reflections. Part of keeping your wall
evenly lit is keeping your subject's shadow from falling across it. To
do this you need to position the talent at a distance of at least a few
feet from the screen, and light him separately using three point
lighting. We offer green screen set-up services, call today!

We will set-up your Green Screen and Lighting if you use a Live Video Production Software, we offer training,
how to bring
inputs into your software, set-up presets, titles, lower thirds, virtual sets,
images, photos, overlays, audio, videos, PowerPoint's, NDI, desktop
capture, cameras, and more. We offer Laptop Key Programming, we will
program your laptop keys to work with your software, your iPad, or Android
Tablet.